The present invention relates to blood processing systems and more particularly concerns the overall arrangement and individual components of an extracorporeal system that integrates blood gas separation, cardiotomy reservoir, venous reservoir, oxygenation, temperature control and pumping of the blood.
In membrane oxygenators of the type shown in the patents to Bentley U.S. Pat. Nos. 4,196,075 and 4,094,792 and the patents to Kolobow U.S. Pat. No. 3,489,647, Friedman U.S. Pat. No. 3,792,978, Leonard 3,927,980 and Bellhouse 4,182,653, carbon dioxide from blood on one side of the membrane passes through the membrane into a gaseous oxygen on the other side and oxygen is taken up through the membrane by the blood. Membrane oxygenators of the prior art, although avoiding some problems and limitations of these oxygenators, such as bubblers, employing a direct blood gas interface, introduce a number of problems and disadvantages unique to the membrane-type configuration.
In priming the oxygenator to get it ready for use, a priming fluid must fill the chamber and be recirculated to remove entrapped air. Such oxygenators often require ten minutes or more to insure removal of all entrapped air. In the course of an operation, the extracorporeal blood processing system is often called upon first to lower blood temperature and then to raise blood temperature. Accordingly, most systems employ a heat exchanger for this purpose. Such heat exchangers of prior systems, whether integral with the mass transfer oxygenator, or separate therefrom, are complex and costly, making the manufacture of a disposable system expensive. Prior membrane systems employ high blood pressure differentials that tend to increase blood trauma and lysing of cells.
Excessive arterial blood line pressure or introduction of air into the arterial blood must be avoided at all cost, and improved safety in these areas is always needed.
Although an oxygenator is generally employed with a separate cardiotomy reservoir and venous reservoir, few systems are available that optimally arrange and coordinate these components. Further, cardiotomy reservoir and blood gas separators themselves may introduce excessive blood trauma because of undue forces exerted upon the blood. They may require a separate and independent pump for the reservoir and fail to provide adequate control and regulation of storage and flow. Ventricular pumps employed in some prior systems are difficult to free of entrapped air and peristaltic pumps in prior systems may be a source of additional blood trauma or excess pressure. Thus, there is a need to minimize such problems and provide a fully integrated system having a blood gas separator, a readily regulated cardiotomy storage reservoir, a venous reservoir, and a mass transfer system or oxygenator and heat exchanger of high reliability and relatively low cost.
Accordingly, it is an object of the present invention to eliminate or minimize above-mentioned problems and to provide an extracorporeal blood processing system and components thereof which are efficient, reliable and safe and which minimize blood trauma.